Glazing panels in motor vehicles today have a number of additional electrical devices such as an antenna, glazing panel heater, and the like.
Through the introduction of an electrically functional component or an electrically functional layer coupled with a glazing panel, automotive glazing can be provided with various functions. The electrically functional components are, for example, antenna elements, solar cells or electrochromic coatings. Through insertion of thin metal wires or application of an electrically heatable coating, a heating function can be obtained. These electrically functional component or layer need to be connected for example to a power source or to an amplifier thanks to at least an electrically conductive connector. The electrical connectors are attached before the glazing panel is installed in the motor vehicle.
The attachment to a glazing panel occurs in that an electrically conductive connector provided with solder material is placed on the contact surface of the glazing panel and is then heated so that the solder material melts with the contact surface of the glazing panel.
Traditionally, the connectors are soldered to an electrically functional component or an electrically functional layer with a lead-based solder material because lead is a deformable metal and minimizes mechanical stress between the connector and the substrate due to difference of thermal expansion of the connector and the substrate resulting from changes in temperature. More specifically, differences in coefficients of thermal expansion between the connectors, which are typically made of a good conductive material such as copper, and the substrates cause the mechanical stress. In case of a glass substrate, such stress may result in cracking or other damage to the substrate, which is typically made of glass. Lead-based solder material, typically comprises tin (Sn) and lead (Pb). The lead decreases the radical reaction rate between tin in the solder and the electrically functional component or the electrically functional layer, generally consisting of a high silver (Ag) content, allowing for good solderability. However, it is known that lead may be considered an environmental contaminant. Thus, there is a motivation in many industries, particularly the automotive industry, to move away from all uses of lead in vehicles. On top of that, the EU legislation, e.g. the current “End of Life” Vehicle Directive (ELV Directive) 2000/53/EC prohibits certain hazardous substances such as lead. The main impetus for the industry to leave lead behind is a ban on lead in electronics imposed by the European Union. Under the Restriction of Hazardous Substances directive, as of 1 Jul. 2006 lead must be replaced by other substances in electronic equipment. (The directive also bans mercury, cadmium, and hexavalent chromium.) Any electronic components bound for Europe are subject to the ban.
The use of lead-free solder materials is common in the microelectronics and plumbing industries. Such materials are for example described in EP0704727B1 and U.S. Pat. No. 4,758,407B which are representative patents from each of these respective industries.
The use of lead-free solder materials is expanding into other industries, including the automotive industry. Such use is for example described in US publication US20070224842A1.
Conventional solder materials have been proposed to replace the lead in the solder material. Such materials comprise commonly a high level of tin, along with small amounts of silver, copper, indium and bismuth. However, such materials increase radical reaction rates between the tin-rich solder material and the silver of or added to the electrically functional component or the electrically functional layer, resulting in poor solderability. These conventional materials do not absorb the mechanical stress between the connector and the substrate due to thermal expansion of the connector and the substrate resulting from changes in temperature, which tends to crack or otherwise damage the substrate. Further, many alternative materials for the connector are difficult to solder, making it difficult to sufficiently adhere the connector to the electrically functional component or the electrically functional layer such as antenna on the substrate. As a result, other techniques would be required in order to sufficiently adhere the alternative materials to the electrically functional component or the electrically functional layer such as antenna on the substrate.
For example, U.S. Pat. No. 6,253,988 discloses solder material compositions including high amounts (or large amounts) of indium due to a low melting point, malleability, and good solderability to the electrically functional component or the electrically functional layer. However, solder material compositions including indium may have very soft phases, and the solder material compositions exhibit poor cohesive strength under stress. Because these other conventional materials are insufficient, there is a need, particularly, to find an electrically conductive connector soldered with a lead-free solder material.
The present invention relates to a glazing panel more particularly a vehicle glazing comprising an electrically functional component or an electrically functional layer linked through an electrically conductive connector. A such electrically functional component or electrically functional layer is for example an antenna.
An antenna is an electrical device which converts electric power into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter supplies an electric current oscillating at radio frequency (i.e. a high frequency alternating current (AC)) to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals that is applied to a receiver to be amplified.
Antennas are essential components of all equipment that uses radio. They are used in systems such as radio broadcasting, broadcast television, two-way radio, communications receivers, radar, cell phones, and satellite communications, as well as other devices such as garage door openers, wireless microphones, Bluetooth-enabled devices, wireless computer networks, baby monitors, and RFID tags on merchandise.
Typically, an antenna consists of an arrangement of metallic conductors, electrically connected (often through a transmission line) to the receiver or transmitter. An oscillating current of electrons forced through the antenna by a transmitter will create an oscillating magnetic field around the antenna elements, while the charge of the electrons also creates an oscillating electric field along the elements.
In the automotive field, antennas are used to send and/or to receive information such as radio, TV or cell phone signals (GSM) but also to communicate with the vehicle, i.e. to be able to open car doors without having to insert the key, with other vehicles, i.e. to keep a distance between to vehicle, or with the environment, i.e. tolls, traffic lights, . . . .
Antennas may be assembled within the glazing, i.e. windshield, backlite, sidelite or sunroof or fixed in the carbody, such as roof. There are different antenna systems used in a vehicle.
The antenna size is usually fraction of the wave length (λ) of its operating frequency, typically λ/2 or λ/4. Additionally, the presence of neighbor dielectric medium reduces the dimension of the radiator by a factor of √{square root over (∈r)} where ∈r is the relative permittivity of dielectric material.
Modern cars may contain multiple antennas for analog audio broadcasts (amplitude modulated (AM—0.5-1.7 MHz) and frequency modulated (FM—76-108 MHz), global positioning system (GPS—1575 MHz) data, cellular phone communication, e.g. global system for communication (GSM—800/1800 MHz), long term evolution (LTE—800/1800/2600 MHz), digital audio broadcasting (DAB—170-240 MHz), remote keyless entry (RKE—315/433 MHz), television reception, tire pressure monitor system (TPMS—315/433 MHz), automotive radar (22-26 GHz/76-77 GHz), car to car communication (C2C—5.9 GHz), etc.
A first system is well-known and described in U.S. Pat. No. 8,519,897B2. Low-profile antenna assembly or Shark fin type car antenna assembly, are configured for using with AM/FM radio, satellite digital audio radio services (SDARS), global positioning systems (GPS), digital audio broadcasting (DAB)-VHF-III, DAB-L, Wi-Fi, Wi-Max, and cell phones. In some example embodiments, the antenna assemblies include at least two antennas co-located, for example, on common chassis of the antenna assemblies, under common covers of the antenna assemblies. Such antennas are commonly placed on roofs, hoods, or trunks of automobiles to help to ensure that the antennas have unobstructed views overhead or toward the zenith.
A second well-known system is backlite antenna system utilizing defogger elements already encapsulated in the back window of the vehicle as antenna elements to receive the AM and FM broadcasts. Examples of such backlite antenna systems can be found in U.S. Pat. No. 5,293,173 or in U.S. Pat. No. 5,099,250. For the known combination defogger/antenna element systems embedded in rear windows of vehicles, it has been necessary to incorporate two bifilar or toroidal chokes between the elements and the vehicle DC power supply so as to separate the antenna signals from the high current signals that heat the elements.
A third system is well-known and described in US publication US2014104122A1. This system consists of a window assembly with an antenna element including wire or transparent coating disposed within the glazing. This type of antennas is generally configured to receive linearly polarized radio frequency (RF) signals. Specifically, the linearly polarized RF signals which the antenna element may receive, in a non-limiting manner, AM, FM, RKE, DAB, DTV and cell phone signals.
With the evolution of technologies, vehicles are equipped with a lot of antennas to be able to communicate (receiving or emitting information). Some are fixed on the carbody, others are placed on the glazing panels of glass.
Classical automotive broadcast low frequency antennas placed on glass (the second or the third type of antennas) are electrically fed, powered and connected by a single element as described in the PCT publication WO2004068643.
Classically, this element is physically and electrically connected to the antenna by a single crimp soldered within an area of silver print. For example, a 10 mm by 10 mm silver print area is printed on a backlite and is linked to a wire antenna. The element could be a wire, a pigtail, a copper line or a MQS flat cable connected to an active amplifier.
The soldering of this type of antennas is not critical as long as it fits inside, the said predefined area and has no impact on the functionality and performance of these low frequency antennas since it is a small fraction of their wavelength.
In the case of higher frequency systems, so with much shorter wavelength, two problems appear.
The first problem is due to the single wire line. A single wire line is not suitable to transport the signal and to receive the power and waves. For efficient power transmission and transportation at higher frequencies, a coaxial cable is needed. The said coaxial cable corresponds to an assembly comprising a central metallic thin line or central pin, conductor, coming through, inside a cylindrical dielectric plastic material, that is also covered by a cylindrical metallic shield, metallic grid as a ground plane. This assembly is covered finally by an insulating layer. The signal, wave, voltage, current, will circulate between the central pin and the metallic shield of the coaxial cable.
Generally, antenna for these high frequencies comprises at least two parts which are connected to the coaxial cable. The metallic shield of the coaxial cable is connected to the first part of the antenna (for example the ground) and the central pin is connected to the second part of the antenna in such a way to receive or transmit an electrical potential difference, voltage between these two parts of the antenna.
The second problem is due to the soldering. Antennas at higher frequency have small wavelength. So the precision of the soldering at higher frequency is or may be strict since even small fluctuations are still comparable to the wavelength.
For these reasons, wideband antennas need to be connected to a specific cable such as a coaxial cable. This coaxial cable needs to be connected on one hand to the ground of the antenna and on the other hand to the second part of the antenna. For that, the cable is connected to the antenna via a connector that connects the metallic shield of the coaxial cable to the ground of the antenna and also allows the central pin to be connected to the other part of the antenna.
The following description relates to an automotive glazing but it's understood that the invention may be applicable to others fields like architectural glazing which may provide electrically functional component or an electrically functional layer coupled with a pane of glass.